Interleukin 6 – no innocent bystander

A molecular model of Interleukin-6

If someone was repeatedly found near the scene of a crime, you’d expect the police would, at some point, begin to suspect that they might be more than just an innocent bystander.

And so it turns out, clumsy crime analogy aside, that a molecule involved in promoting inflammation – the body’s natural defence against injury and infection – might actually be a key player in cancer development.

Interleukin 6 (IL-6 for short) is described by Wikipedia as “a pro-inflammatory cytokine secreted by T cells and macrophages to stimulate immune response to trauma, especially burns or other tissue damage leading to inflammation.”

What this means, in layman’s terms, is that IL-6 is a molecule produced by your white blood cells when you get injured, to cause the injured area to swell up. Inflammation like this is extremely important in helping your immune system deal with problems. Amongst other things, it increases blood-flow to the area, encourages cells to divide and repair themselves, and makes your blood vessels ‘leaky’ so that white blood cells can enter the surrounding tissue and combat any nasties.

So far so good, but what’s this got to do with cancer?

Several lines of evidence are pointing to the fact that inflammation, gone wrong, might be an important step in cancer development. According to this theory, ‘acute’ inflammation (i.e. inflammation in short bursts) is a good thing, but ‘chronic’ inflammation – low-level, long-term inflammation caused by cigarette smoke, a bad diet, etc, is most definitely bad. (For more info on the evidence behind this, read this excellent article in Science from a few years back.)

What makes this interesting, to us at least, is that there have been a few stories in the media and elsewhere recently that link IL-6, a central player in inflammation, to cancer.

Firstly, on 9th July, we reported on a US group who found that differences in IL-6 levels between male and female rats might account for the difference in liver cancer rates between the two sexes (liver cancer is far mroe common in men than in women).

Then, yesterday, a paper was published that linked IL-6 to the ras genes. Ras genes are a very important family of genes that regulate how, where and when a cell divides. Several studies have shown that about a quarter of human cancers have mutations in these genes , and many other cancers have faults (mutations) that make ras more active. According to the recent research, hyperactive ras tells a cell to make more IL-6.

Since researchers have been unable to find a suitable way to target faulty ras genes with drugs, and since IL-6 seems to be linked to ras, inflammation, and cancer development, this raises the intriguing possibility that somehow targeting IL-6 levels with drugs might be an avenue worth pursuing.

Several labs around the world are looking at doing just this, and its going to be worth following how they get on.

Almost every day we hear of a new molecule that may be a new tool in the fight against cancer, but more often than not, such ‘drug targets’ prove to be less than ideal. In the case of IL-6, the story might be a little different.

Henry